The two countries have drawn closer in recent years and tout their friendship as having "no limits". Both share hostile relations with US-led Western defence alliance NATO.

Beijing has further strengthened its diplomatic, economic and military ties with Moscow since the start of the Russian invasion of Ukraine in February 2022.

China, which has never condemned the invasion, maintains it is a neutral party to the conflict. But Western leaders have criticised it for giving political and economic support to Russia, including trade in goods that have both civilian and military uses.

"According to the annual plan and the consensus between China and Russia, naval vessels of China and Russia recently carried out their fourth joint maritime patrol in the western and northern Pacific Ocean," the Chinese defence ministry said in a statement on Sunday.

"This operation is not targeted at any third party and has nothing to do with the current international and regional situation," it added.

No details were provided on the Pacific manoeuvres, including the ships' routes, their exact locations or the nature of the forces involved.

On Friday, China said it was also conducting drills with Russia -- known as Joint Sea-2024 -- along its southern coast.

This came after NATO leaders declared Beijing had "become a decisive enabler" of Moscow's war in Ukraine, and after Japan warned of a growing threat from Beijing's strong ties with Moscow.

Beijing has rejected the criticisms.

The drills in the waters and airspace around Zhanjiang, a city in southern Guangdong province, are "to demonstrate the resolve and capabilities of the two sides in jointly addressing maritime security threats and preserving global and regional peace and stability", the ministry said.

The Russian defence ministry said Saturday that two of its warships had arrived in Zhanjiang to take part in the joint naval drills, with an initial phase taking place from Monday to Wednesday.

The Pacific is a hotbed of international tensions due to sovereignty disputes between Beijing and several of its US-backed neighbours, such as Japan, the Philippines and Taiwan.

China and Russia hold joint military exercises regularly but their level of interoperability is greatly inferior to that of NATO, the European Union Institute for Security Studies said in a report in early July.

In 2023, ships from the two countries took part in a naval exercise off the US state of Alaska.